It's easy to get confused about the many tests available to investigate possible heart disease. Let's review some of the more common tests, along with what they can tell us about the condition of the heart.
The simplest test is an electrocardiogram, also called an ECG or EKG. In an ECG, sticky electrode pads are placed on the patient's chest, and are then connected by wires to a monitor that records the electrical signals from the heart. An ECG provides a lot of information about how well the heart is coordinating its beats and the approximate size of various parts of the heart.
The test also looks for characteristic features that suggest a patient has had or may currently be having a heart attack. But ECGs do not provide much information about your risk of having a heart attack in the future.
An echocardiogram is an ultrasound picture of the heart. Like ultrasounds of developing babies, echocardiograms provide amazingly detailed, moving pictures of the heart as it is beating. This non-invasive technology is especially useful for measuring the size, structure, and function of the heart valves and muscles, including how effectively each side of the heart is pumping blood. Like ECGs, echocardiograms tell us mainly about past and present conditions, not future risks.
Two main types of tests are used to look for signs of a possible future heart attack: functional tests and anatomic tests. Stress tests are used to determine how well the heart functions under exertion - that is, if the heart is receiving enough blood and oxygen to meet its needs. These tests, however, don't tell us anything about the condition of the arteries that are supplying the heart with blood.
Anatomic tests, like cardiac catheterization, allow doctors to evaluate how open or blocked the coronary arteries around the heart are. But these tests don't tell us much, if anything, about the effect such blockages have on the heart's ability to function.
In a cardiac catheterization, also called a coronary catheterization or coronary artery angiogram, a catheter is inserted into an artery (usually in the groin) and then slowly snaked all the way up through the aorta and into the coronary arteries.
After the catheter is in place, a contrast agent (often called dye) is injected into the blood vessels while doctors use X-ray imaging to see exactly where and how severe any obstruction(s) is/are. If considered safe and appropriate, these blockages can be treated immediately with angioplasty, stents, or other techniques that hopefully will correct the obstruction. Cardiac catheterization is often necessary and safe, but because it is an invasive procedure that carries some risks, researchers continue to work on developing alternatives.
A newer anatomic heart test uses computed tomography (CT) to estimate how much arterial plaque is present. Expressed in the coronary CT calcium score, this test measures calcified deposits in the walls of the coronary arteries. Most plaque contains calcium deposits, so there is a pretty good correlation between this measurement of calcium and the amount of actual coronary artery narrowing.
This test is safer, faster, and less expensive than cardiac catheterization, but occasionally over- or underestimates the amount of plaque. I find it most useful in patients for whom a stress test has been inconclusive, and we need more information before committing to a catheterization procedure.
